1. Field
Embodiments described herein generally relate to methods and system regarding manufacture of substrates used in integrated circuit (IC) packaging.
2. Background Art
Integrated circuit (IC) devices typically include an IC die housed in an IC package. The IC package is used to protect the IC die from the surroundings and to facilitate electrical interconnection between the IC die and a printed circuit board (PCB) on to which the device is mounted. Through the PCB, the IC die can be electrically coupled to other IC devices mounted on the PCB.
IC packages typically include a substrate on which the IC die is mounted. The substrate is coupled to electrically conductive regions on the IC die (e.g., through wirebonds or solder bumps). The substrate can include multiple metal layers that are used to facilitate interconnection between the IC die and the PCB and with other IC dies located in the same device. The metal layers are separated by dielectric layers. Specifically, the substrate typically includes a relatively thick core dielectric in the center of the substrate on which the first pair of metal layers are formed and relatively thin dielectric layers that separate the remaining metal layers.
When signals are passed from one metal layer to another, e.g., using a via, the quality of signal degrades, with the amount of degradation being related to the thickness of the dielectric layer that separates the pair of metal layers. Because the core dielectric is relatively thick, signals that are especially sensitive to degradation often cannot be passed through the core dielectric. Thus, the metal layers formed on the side of the core dielectric opposite to the side on which an IC die is located are often wasted as they cannot be used to facilitate interconnections.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears.